The present invention relates to an electromagnetic actuator used mainly in an automotive internal combustion engine.
A conventional electromagnetic actuator for automotive internal combustion engines is made up of a large number of parts as disclosed e.g. in Japanese patent publication No. 11-93629. For these parts, there is no disclosure about their material and attempts for lessening their weights.
Because the electromagnetic actuator disclosed in the abovesaid publication is provided for each valve, its weight directly influences the total weight of an internal engine. When it is used in an automobile, its weight influences the fuel consumption and the engine performance. Thus reduction in weight of the electromagnetic actuator is a large problem.
Since the size and weight of the parts are proportional to the electromagnetic force required to the electromagnetic actuator, parts in the magnetic circuit are needed which generate electromagnetic force efficiently, to achieve reduction in weight of the electromagnetic actuators. But conventional magnetic circuit parts using silicon steel plates had low saturated magnetic flux density and production of eddy current decreased response of the actuator. Thus increase in the size and weight of the magnetic circuit and the actuator was inevitable for greater performance flexibility.
An object of the present invention is to improve the electromagnetic performance of a stator as one of magnetic circuit parts forming an electromagnetic actuator used in an automotive internal combustion engine, thereby reducing the size and weight of an electromagnetic actuator.
According to this invention, there is provided an electromagnetic actuator comprising a pair of electromagnets each made up of a stator and a coil, an armature disposed between the pair of electromagnets so as to be reciprocable therebetween, and a first stem provided on one side of the armature for transmitting the movement of the armature to external, the stator being formed by powder molding.
The use of a metal powder molded body as a stator improves the electromagnetic properties of the stator and makes it possible to obtain a more compact, light-weight electromagnetic actuator.